1) Field of the Invention
The present invention pertains to watches comprising a solar time display. The management of time, on our planet, is nowadays based on a time reference, called GMT and on a structure of time zones within which the civil time is the same everywhere. Such a definition of time greatly simplifies human relationships. This time is, however, offset with respect to solar time, dependent on the longitude of a place, and which is displayed by sundials. The goal of the present invention is to propose a watch making it possible to ascertain both the civil time and the solar time, for any longitude and in any time zone.
To this end, the watch according to the invention comprises civil time display means, solar time display means and means of correction of the civil and solar time displays. According to the invention, the means of correction are arranged in such a way as to allow a relative manual desynchronization of the civil time and solar time display means. Moreover, this watch comprises means for displaying this desynchronization.
Hence, in order for the watch to actually display the solar time, it suffices that the civil time display means indicate the civil time of a time zone to be taken into account, and the means of display of the desynchronization the difference between the longitude of the middle of this time zone and the longitude of the place in question.
2) Description of Related Art
Admittedly, it is already known to display a desynchronization with reference to the mean solar time. Such a solution is described in U.S. Pat. No. 5,184,333. It pertains to a watch displaying the equation of time, that is to say the difference between the mean solar time and the true solar time. This desynchronization is performed automatically by means of a mechanism making one revolution in a year and driving a cam which controls the display. The information displayed is, in fact, valid only for the median position of a given time zone, everywhere else, the information displayed is erroneous, both for the true solar time and for the mean solar time.
Additionally, timepieces are known that allow an astronomical bearing to be taken, for example through U.S. Pat. No. 1,459,710, which describes a small clock that displays both the solar time and the sidereal time, thus allowing a bearing to be taken either at night or by day, to the extent that the sky is clear.